This book expounds the transcendental realist theory of science and critical naturalist social philosophy that have been developed by Bhaskar and are used by many contemporary social scientists. It defends Bhaskar's view that the possibility and necessity of experiment show that reality is structured and stratified, his use of this idea to develop a non-reductive explanatory account of human sciences, and his notion that to explain social structures can sometimes be to criticize them. After a discussion of the uses of critical realism in controversial areas of social science, Bhaskar's optimism about the prospects of human sciences is criticized